1. Technical Field
The present disclosure relates to a noise reduction apparatus for reducing noises.
2. Related Art
JP-A-2-285799 (Patent Document 1) discloses a basic configuration of a noise reduction apparatus. This noise reduction apparatus outputs a control sound of which phase is opposite to a noise from a noise source in a noise reduction position (control point). As a result, noises at the control point are reduced.
JP-A-7-253788 (Patent Document 2) discloses a noise reduction apparatus that estimates a noise reduction amount and controls an ON/OFF state of the noise reduction apparatus according to the estimated noise reduction amount. Specifically, the noise reduction apparatus has a speaker for outputting a control sound, a first microphone provided on a noise source side of the speaker, and a second microphone provided on an opposite noise source side (for example, the control point) of the speaker. The noise reduction apparatus detects a noise when the noise source operates and a noise (dark noise) when neither the noise source nor the noise reduction apparatus operates through the respective microphones, and estimates the noise reduction amount based on the detected noises. The noise reduction apparatus controls the ON/OFF state of the noise reduction apparatus according to the estimated noise reduction amount.